Method of molding a bottle-shaped container of synthetic resin

Abstract

A tubular parison for molding a bottle-shaped container of biaxially oriented synthetic resin and a bottle-shaped container blow-molded from the tubular parison for filling, for example, drinking water containing carbon dioxide gas or the like. The tubular parison is advantageously formed so that the shoulder and bottom forming portions are thinner by a predetermined ratio than the body thereof. Thus, the bottle-shaped container blow-molded from the tubular parison is much stronger in construction.

What is claimed is: 
     
       1. A process for forming a bottle-shaped container, comprising: heating a parison of biaxially orientable resin to a temperature for biaxial orientation blow molding; then   longitudinally stretching and axially orienting the parison in a blowing mold, said parison comprising, in unstretched condition:   an upper port forming portion;   a body of substantially uniform thickness;   a shoulder forming portion located between the upper port forming portion and the body; and   a bottom forming portion, wherein the shoulder and bottom portions each have a thickness which is about 80% or less than that of said body, said shoulder forming and bottom forming portions being reduced further in thickness and being the portions of the parison mainly oriented by said longitudinal stretching; and then   blowing said longitudinally stretched parison to a bottle shape to biaxially orient the resin of the body;   the shoulder forming and bottom forming portions undergoing an amount of orientation which approaches that undergone by the body.   
     
     
       2. A process as claimed in claim 1, wherein said longitudinal stretching is performed by a slidable push rod located in the interior of said parison. 
     
     
       3. A method as claimed in claim 2, wherein said push rod is hollow and perforated to provide air for said blowing. 
     
     
       4. A method as claimed in any one of claims 1 through 3 wherein said parison body is substantially cylindrical.